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Letter to Kenneth Gibson MSP from Naval Architect Euan Haig

Dear Mr Gibson,

I am a Naval Architect with long experience in design, procurement, and construction of a variety of vessels. I have taken an interest in Scottish ferries because of the scale of waste and the bad decision-making at every level involved in Ships 801/802 at Fergusons. I am appalled at what it says about Scotland. I have read the RECC Report carefully and consider it a restrained, balanced, and fairly complete evaluation of the mistakes and who made them. I especially support the view that future ferry procurements must not follow the path of 'business as before'. But CMAL is doing exactly that in the New Islay Ferry.

I receive material from a range of sources, one of which is the Arran Ferry Action Group. It has copied me your 'Replies to Candidate Questions' which i read with interest. One of the most disturbing features of this whole affair is the erratic professionalism of those in the various organisations, as is sometimes made clear by their results. Engineers frequently remind themselves that if someone cannot explain their subject effectively in simple language then he might not understand it himself. I therefore draw your attention to Robbie Drummond's statement in your 'Reply' that '.....catamarans are less stable.....' presumably than Monohulls. It is so wrong that i would like to confirm with you that he actually said that.

Catamarans are many times MORE stable than monohulls. Their reserve of stability enables them to survive flooding after grounding or collision that monohulls could not, especially monohull ferries with great top-hamper. Monohull ferries are infamous for their propensity to invert suddenly and unpredictably although only partly flooded, thereby killing a lot of people quickly.

I have become aware that there is a simple prejudice against catamarans. Catamarans can be perfectly legitimate solutions to the needs of a ferry service and it is mistaken to be 'against' merely on the basis of opinion. Catamarans roll and pitch differently from monohulls. The comparison here should not be between catamarans and weatherly monohulls; it should be between catamarans and the typical CalMac monohull.

I am aware CMAL has made another misleading statement. Kevin Hobbs was quoted in The Scotsman in January as saying that the New Islay Ferry would be wider than the vessel it replaces and '..... increased beam helps the hydrodynamics of a ship, which then reduces the fuel'. That too is rubbish. Naval Architects and scientists have expended thousands of man-years measuring the resistance of various ship forms at various speeds since the science was established in the 1860's. Denny's Shipyard in Dumbarton was a world leader in this, with one of the first Towing Tanks. It is still there. I saw it in use. The hydrodynamic part of design can now be done by Computational Fluid Dynamics. I am not aware of any single vessel or type of vessel whose resistance was reduced by increasing beam. Resistance increases with increasing beam.

I am concerned that there might be a pattern of disinformation here whether by accident or design. Politicians and others without professional knowledge rely on accurate advice from professionals. False information makes it impossible for non-professional decision-makers to perform correctly. Is a factor making Scottish ferries cost so much to build and so uneconomic to operate? Concerning the last, the operating subsidy for Scottish Ferries has risen at 12 to 14% every year for the last 15 years or so and now stands at about £200M pa.

The typical open-water CalMac ferry is prone to service cancellation in bad weather, whether at Arran or Islay or else where. (I mention Islay because CMAL is pressing with ' business as before' for a new ferry.) Cancellations are strongly influenced by sea-state at harbour mouths where seas are rough because of shallow water. The sea state in deep water is often a lot better than inshore. A strong wind blowing against a strong tide will make everything worse. CalMac ferries are not designed to be weatherly; there is much about them that worsens their response to bad weather.

Their design packs as much ship as possible onto the hull at waterline. The resulting ship is wide, with bluff bows, high flat sides, and high superstructure giving high windage. These are ships that will roll heavily in beam seas and side winds. The hull shape does not slice into waves easily. Pitch angles can be expected to be greater and motions more abrupt than for vessels with fine bows including catamarans. Vessels are more controllable when driving out of a harbour against a strong wind and waves than when pushed into a harbour by a following gale with following waves. High superstructure does not help. It would make sense to design vessels to relate more easily to wind and waves but there is no evidence CMAL considers that.

The New Islay Ferry will be just as prone to weather cancellation as the present vessels. This often causes short shippings in sailings immediately after cancellations until the backlog is clear. Despite its high cost NIF will be no more reliable in bad weather than existing vessels. Some short shippings are caused bypass in commercial vehicle traffic, not bad-weather cancellations, especially the mid-afternoon sailing from Port Askaig Modest increases in vehicle traffic will sooner or later result in the same level of short shippings from this cause. This expensive new vessel will fail to be an enduring solution.

Oceanography plays a part in this. Storms generate waves of all wave-lengths. Mathematics represents the behaviour of sea-waves accurately. It explains why large waves refract and become parallel to the shore where they eventually break. This is relevant to a vessel entering or leaving a harbour set in a shelving shoreline such as Troon, Ardrossan, or Port Ellen. (I have personal experience of every one in bad weather.)

The underwater topography of Islay at Port Ellen goes a long way to explain the sea state on the approach to the harbour. Port Ellen is in a partly-enclosed harbour at the top of a submarine apron rising from the sea-bedr. The apron refracts waves with long wave-lengths up the apron whilst slowing them and increasing their height. Waves with short wave-length will not refract (change direction) until they are in shallow water. The result is a tendency for confused sea. Strong wind against strong tide makes everything worse.

A typical high-sided, high superstructure CalMac ferry with all its windage is about the worst possible style of vessel for these waters, indeed for the entire route along the coasts of Jura and Islayy. The height of superstructure magnifies perceived ship motions because of distance from the pitch and especially the roll axis.

Catamarans can have their place. A monohull will often roll through angles two or more times greater than the slope of the waves it encounters. A catamaran will rarely do so because it is more stable. A monohull's natural frequency of roll might often be the same as the frequency of wave encounter and this can further amplify roll angle. This will rarely happen in a catamaran.

Concerning propensity to seasickness, Robbie Drummond should produce the data on which his remark about seasickness is based. Noting that CalMac does not operate large catamarans, whose data and from what vessels does he summarise? What data does he have from his own monohulls? Seasickness is related to length of exposure so he needs to give data for trips of comparable duration for comparable catamarans and monohulls. Above all, because propensity to seasickness is indeed related to voyage length, he has given another powerful reason to serve the Islands on the shortest and most sheltered routes possible whatever the style of vessel.

The south coasts of Islay and Jura are exposed and seasickness is likely in bad weather. So why not move the service to a short and sheltered route, say to the east coast of Jura? That would transform the reliability, speed and flexibility of the service, and permit it to be provided by smaller, cheaper vessels, bought quickly into service. New roads are cheap in comparison with the costs of building and operating large CalMac ferries. Unlike a new ferry they would be an enduring solution and they would permanently improve the economy of the areas where they run. If the level of traffic on a short route increases with time the demand can easily be met by running more services with the same vessels.

The ferry needs to be better matched to the route, and the route needs to be as short as possible for passenger comfort and avoidance of the high costs of moving vehicles by sea. CalMac's policy of a small number of large ships is the cause of unreliability of service, high ship costs, high operating costs, and inflexibility.

This is a vast subject and I have compressed a lot into this email. That risks distortion. It all needs better explanation and quantification.

A vast amount of Taxpayers' money has been misused on CalMac's vessels and routes because the wrong kind of vessel has been bought in the wrong way. I consider I would be in neglect of the ethical standards of my profession if I failed to speak out where matters are so wrong. I will of course copy this to the Arran Ferry Action Group whilst awaiting your reply concerning Robbie Drummond's statement to you. I will also contact Mr Porteous of the Islay Ferry User Group because this email involves Islay and Jura.

Best wishes,
Euan Haig C Eng, FRINA, RCNC

About Us

The current state of our lifeline ferry service shows it is not fit for purpose in terms of reliability, resilience and infrastructure. The Arran Ferry Action Group is a new and fully representative lobbying group, set up to represent Arran interests in demanding service improvements and accountability in future investment decisions.

 

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Arran Ferry Action Group

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Brodick
Isle of Arran
KA27 8AJ
Scotland
United Kingdom

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